loss of sex drive and pain during sex

So this past month I have had almost no sex drive when i usually have a very high libido. It's been painful when my SO and i have sex to the point to where i've had to tell him to stop a couple of times. I can tell that it's really getting to him and it's really frustrating me too. This is so unlike me. Any ideas ladies? I just had my period this past week if that helps any.

Please help.